Two potential fish glycerol-3-phosphate phosphatases

Glycerol Is an Osmoprotectant in Two Antarctic Chlamydomonas Species From an Ice-Covered Saline Lake and Is Synthesized by an Unusual Bidomain Enzyme

Glycerol, a compatible solute, has previously been found to act as an osmoprotectant in some marine Chlamydomonas species and several species of Dunaliella from hypersaline ponds. Recently, Chlamydomonas reinhardtii and Dunaliella salina were shown to make glycerol with an unusual bidomain enzyme, which appears to be unique to algae, that contains a phosphoserine phosphatase and glycerol-3-phosphate dehydrogenase. Here we report that two psychrophilic species of Chlamydomonas (C. spp. UWO241 and ICE-MDV) from Lake Bonney, Antarctica also produce high levels of glycerol to survive in the lake's saline waters. Glycerol concentration increased linearly with salinity and at 1.3 M NaCl, exceeded 400 mM in C. sp. UWO241, the more salt-tolerant strain. We also show that both species expressed several isoforms of the bidomain enzyme. An analysis of one of the isoforms of C. sp. UWO241 showed that it was strongly upregulated by NaCl and is thus the likely source of glycerol. These results reveal another adaptation of the Lake Bonney Chlamydomonas species that allow them to survive in an extreme polar environment.

Glycerol-3-phosphate dehydrogenase (GPDH) gene family in Zea mays L.: Identification, subcellular localization, and transcriptional responses to abiotic stresses

Glycerol-3-phosphate dehydrogenase (GPDH) catalyzes the formation of glycerol-3-phosphate, and plays an essential role in glycerolipid metabolism and in response to various stresses in different species. In this study, six ZmGPDH genes were obtained by a thorough search against maize genome, and designated as ZmGPDH1-6, respectively. The structural and evolutionary analyses showed that the ZmGPDHs family had typical conserved domains and similar protein structures as the known GPDHs from other plant species. ZmGPDHs were divided into NAD+-dependent type A form (ZmGPDH1-5) and FAD-dependent type B form (ZmGPDH6) based on their N-terminal sequences. Four full length ZmGPDHs were fused with GFP fusion proteins, and their subcellular localization was determined. ZmGPDH1 and ZmGPDH3 were located to the cytosol and mainly recruited to the surface of endoplasmic reticulum (ER), whereas ZmGPDH4 and ZmGPDH5 were located in the chloroplast. The transcriptional analysis of the ZmGPDHs in different maize tissues revealed relatively high level of transcripts accumulation of ZmGPDHs in roots and early stage developing seeds. Furthermore, we examined the transcriptional responses of the six GPDH genes in maize under various abiotic stresses, including salt, drought, alkali and cold, and significant induction of ZmGPDHs under osmotic stresses was observed. Together, this work will provide useful information for deciphering the roles of GPDHs in plant development and abiotic stress responses.

Glycerol-3-phosphate phosphatase/PGP: Role in intermediary metabolism and target for cardiometabolic diseases

Metabolic diseases, including obesity, type 2 diabetes, and metabolic syndrome arise because of disturbances in glucose and fat metabolism, which impact associated physiological events such as insulin secretion and action, fat storage and oxidation. Even though, decades of research has contributed to our current understanding of the components involved in glucose and fat metabolism and their regulation, that led to the development of many therapeutics, there are still many unanswered questions. Glycerol-3-phosphate (Gro3P), which is formed during glycolysis, is at the intersection of glucose and fat metabolism, and the availability of this metabolite can regulate energy and intermediary metabolism in mammalian cells. During the course of evolution, mammalian cells are assumed to have lost the capacity to directly hydrolyze Gro3P to glycerol, until the recent discovery from our laboratory showing that a previously known mammalian enzyme, phosphoglycolate phosphatase (PGP), can function as a Gro3P phosphatase (G3PP) and regulate this metabolite levels. Emerging evidence indicates that G3PP/PGP is an evolutionarily conserved "multi-tasking" enzyme that belongs to the superfamily of haloacid dehalogenase-like phosphatase enzymes, and is capable of hydrolyzing Gro3P, an abundant physiologically relevant substrate, as well as other metabolites including 2-phosphoglycolate, 4-phosphoerythronate and 2-phospholactate, which are present in much smaller amounts in cells, under normal conditions. G3PP, by regulating Gro3P levels, plays a critical role in intermediary metabolism, including glycolysis, glucose oxidation, cellular redox and ATP production, gluconeogenesis, esterification of fatty acids towards glycerolipid synthesis and fatty acid oxidation. Because of G3PP's ability to regulate energy and intermediary metabolism as well as physiological functions such as insulin secretion, hepatic glucose production, and fat synthesis, storage and oxidation, the pathophysiological role of this enzyme in metabolic diseases needs to be precisely defined. In this review, we summarize the present knowledge on the structure, function and regulation of G3PP/PGP, and we discuss its potential therapeutic role for cardiometabolic diseases.